The SPGB is probably the only avowedly atheist political party in existence.
Not only have we consistently advocated world socialism - a fully democratic society based upon co-operation and production for use -, opposed every single war, opposed every single government and been a democratic and leaderless organization since 1904. We have consistently stated that religion is guff and an anti-social force. This was massively controversial in the early days of the party. The Socialism and Religion (1911) pamphlet is still popular, and recent editions of our journal contain pieces on religion (e.g. here, here and here).